The present invention relates generally to a new engine for use in, for example, personal watercraft. In particular, the present invention relates to a new four-stroke in-line engine that was developed with a view to the future stricter environmental and emission regulations. The engine has a flexible intake manifold that can be configured for use either with a supercharged engine or a normally aspirated engine. Further, the intake manifold is configured such that a flame arrester is positioned therein to prevent the exit of flames from the manifold in the event of an engine backfire.
There is a very popular type of watercraft known as a xe2x80x9cpersonal watercraftxe2x80x9d which is designed to be operated primarily by a single rider. Although this type of watercraft is commonly employed for single riders, frequently provisions are made for accommodating additional passengers although the maximum number of passengers is more limited than conventional types of watercraft.
This type of watercraft is also generally quite sporting in nature and normally accommodates at least the rider on a type of seat in which the rider sits in a straddle fashion. The passenger""s area is frequently open through the rear of the watercraft so as to facilitate entry and exit of the rider and passengers to the body of water in which the watercraft is operating, as this type of watercraft is normally ridden with passengers that are wearing swimming suits.
These personal watercraft are generally quite small so that they can be conveniently transported from the owner""s home to a body of water for its use. Because of the small size, the layout of the components is extremely critical, and this gives rise to several design considerations that are peculiar to this type of watercraft. However, due to its sporting nature it is also desirable if the watercraft is powered by an engine and propulsion device that are not only efficient but also generate sufficient power.
Traditionally, two-cycle engines have been used to power watercraft, including personal watercraft. These engines have the advantage that they are fairly powerful, relatively lightweight, and compact.
One particular disadvantage to the two-cycle engine is its emission content. Two-cycle engines generally exhaust larger quantities of hydrocarbons and other pollutants than four-cycle engines due to cylinder charging inefficiencies and the combustion of lubricating oil among other things. When measures are taken to reduce emissions of the two-cycle engine, other generally undesirable consequences can result, such as an increase in the weight of the engine, a reduction of its power output or the like. With concern for the environment and increasingly strict emissions requirements being instituted by various governing bodies. There is motivation to provide a power plant that reduces exhaust emissions while retaining other advantageous characteristics such as compactness, low weight and high power output.
Four-cycle engines are commonly used as power plants in other applications, such as automobiles. These engines have the advantage that their emissions output are generally desirably lower as compared to a two-cycle engine for a given power output.
U.S. Pat. No. 5,513,606 to Shibata, entitled xe2x80x9cMarine Propulsion Unitxe2x80x9d discloses several embodiments of engines of use in outboard motors. The engines are configures such that the air induction systems are positioned on the side of the engine.
U.S. Pat. No. 5,846,102 to Nitta et al., entitled xe2x80x9cFour-Cycle Engine For A Small Jet Boatxe2x80x9d discloses both two and four cycle engines for a personal watercraft. The intake suction devices of these engines are located on the side of the engine such that the larger four-cycle engine can be located with the personal watercraft.
These references, however, do not disclose an air intake manifold that is capable of being used in either a supercharged engine or a normally aspirated engine. Furthermore, these intake manifolds do not include a flame arrester that is positioned within the air passageway within the intake manifold to prevent engine backfires from exited the manifold.
It is an object of the present invention to provide a four stroke, in-line engine having a compact construction.
It is another object of the present invention to provide a four stroke, in-line engine having a modular construction to permit the interchange of parts between various engine models.
It is another object of the present invention to provide a four stroke, in-line engine having improved exhaust emission characteristics.
It is another object of the present invention to provide a four stroke engine having a narrow and low profile.
It is another object of the present invention to provide a four stroke engine having a low profile valve actuation assembly for controlling the operation of the intake and exhaust valves.
It is another object of the present invention to provide a cylinder head having a low profile to reduce engine height.
It is another object of the present invention to offset the placement of the intake valves and exhaust valves with respect to a vertical axis within the cylinder head to reduce engine height.
It is another object of the present invention to provide an improved spark plug mounting assembly for easy access within the cylinder head.
It is another object of the present invention to provide a Y-shaped intake rocker arm assembly providing compact construction.
It is yet another object of the present invention to provide a four stroke engine having an improved oil collection system and oil holding tank.
It is another object to provide a four stroke engine which combines a closed loop cooling system and an open loop cooling system for enhanced cooling of the engine in accordance with the present invention.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open loop cooling system enhances cooling of the crankcase and cylinder head.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open cooling system lowers the temperature of the exhaust manifold such that the exhaust manifold functions as a heat sink for the crankcase and cylinder head.
It is another object of the present invention to provide a closed loop cooling system for selectively cooling the crankcase and cylinder head of the four stroke engine.
It is another object of the present invention to provide a closed loop cooling system having a selectively operable heat exchanger.
It is another object of the present invention to provide a supercharger for enhanced engine performance.
In accordance with the present invention, a four stroke internal combustion engine is disclosed. The normally aspirated engine includes a crankcase and a cylinder head connected to the crankcase. The crankcase and the cylinder head form at least one cylinder having at least one intake valve and at least one exhaust valve. A valve actuation assembly operates the intake and exhaust valve. The engine includes at least one air intake passageway operatively coupled to each cylinder through the intake valves.
The engine in accordance with the present invention includes an air intake system connected to the cylinder head and operatively connected to the intake passageway. The air intake system includes an air intake manifold having a central air passageway extending between a first end and a second end. At least one passageway extends from the central air passageway to a free end, which is operatively coupled to the intake passageway.
The air manifold has a generally symmetrical construction such that the air manifold can be used in either a normally aspirated engine or a supercharged engine. The air intake manifold includes a first opening in the first end and a second opening in the second end. An end cap is located in one of the first opening and the second opening depending on whether the engine is supercharged or normally aspirated.
When the four stroke internal combustion engine is a normally aspirated engine, the air intake system includes an air inlet located at the first opening of the air intake manifold. The end cap is located in the second opening. A throttle is provided to regulate the flow of air into the air intake manifold. It, however, is contemplated that a carburetor may be used. The throttle is positioned within the air intake passageway. The throttle also includes an idle by-pass, which delivers a predetermined supply of air to the air intake system through the idle by-pass when the engine is operating in an idle operating condition. The engine has an engine control system that is operatively connected to the throttle. The engine control system monitors the engine operating parameters and operates the throttle assembly in response to the engine operating parameters.
When the four stroke internal combustion engine is a supercharged engine, a supercharger is operatively connected to the air intake system. With this arrangement, the supercharger is operatively connected to the air intake manifold through the second opening in the second end. The end cap is located in the first opening. The engine control system is operatively connected to the supercharger. The engine control system monitors the engine operating parameters and operates the supercharger in response to the engine operating parameters.
The engines contemplated in accordance with a fuel injection system associated with the air intake system and operatively coupled to the at least one passageway adjacent the free end. The fuel injection system may include a common fuel rail extending along a top portion of the air intake manifold and at least one fuel injection nozzle extending from the common fuel rail to the at least one passageway adjacent the free end. The engine control system monitors engine the operating parameters of the engine and operates the fuel injection nozzle in response to the engine operating parameters.
The present invention is also directed to a personal watercraft for use by at least one passenger. The personal watercraft includes a hull, a seating assembly for the at least one passenger, and a four stroke internal combustion engine located within the hull. It is contemplated that the personal watercraft may have either a normally aspirated engine or supercharged engine, as described above.